I tried to send a mail to info-gnu (AT ...), w/ From:
ttn@gnu.org and X-Message-SMTP-Method: smtp eggs.gnu.org 587,
but instead of going through as it had done previously (maybe a
month or two ago), i encountered the error:

 gnutls.el: (err=[gnutls-e-invalid-session] La sessione specificata è stata invalidata per qualche motivo.) boot: (:priority NORMAL:%DUMBFW :hostname eggs.gnu.org :loglevel 0 :min-prime-bits nil :trustfiles (/etc/ssl/certs/ca-certificates.crt) :crlfiles nil :keylist nil :verify-flags nil :verify-error nil :callbacks nil)
 gnutls-negotiate: GnuTLS error: #<process smtpmail>, gnutls-e-invalid-session

The mail was signed w/ my GPG key (mentioned below), normally
(just like w/ this mail).

What do i need to do to resolve this?  (This is w/ Gnus v5.13 on
Emacs 21.7.)  TIA for any hints/help.

-- 
Thien-Thi Nguyen -----------------------------------------------
 (defun responsep (query)               ; (2021) Software Libero
   (pcase (context query)               ;       = Dissenso Etico
     (`(technical ,ml) (correctp ml))
     ...))                              748E A0E8 1CB8 A748 9BFA
--------------------------------------- 6CE4 6703 2224 4C80 7502